1. Technical Field
Embodiments of the invention relate generally to control systems for rail vehicles. Other embodiments relate to control systems for positioning trains using rail vehicle traction motors and/or braking systems.
2. Discussion of Art
Rail car switching, shunting, and classification are integral aspects of rail freight operations. These procedures are performed in switching yards or classification yards, which include multiple rail tracks branching from one or more lead tracks and joining together at one or more exits. To maximize operational efficiency, several cars or trains of cars are typically moving simultaneously along different branches within a yard. Due to the presence of multiple stationary rail cars or stub trains on intervening tracks, an operator in a locomotive moving on a first track may not be able to see moving cars on a track branching from the first track. Accordingly, locomotive operators may coordinate their actions via a yardmaster stationed in a control tower overlooking the yard.
Three-way communication between operators and a yardmaster can introduce lag time and error, which can be undesirable while moving multiple pieces of heavy rail equipment. As such, some yards include systems by which a yardmaster may remotely control and coordinate movement of multiple stub trains (“tower control systems”).
Previous attempts to properly position trains relied upon manual intervention to control throttle and brakes while attempting to observe train position, using systems not integrated with a tower control system. For example, to position a train being operated by the tower control system under a speed control mode, the train would have to be unlinked from the tower control system and an onboard crew would have to move the train. Such non-integrated or unlinked controls potentially reduce efficacy of the tower control system.
For trains carrying bulk cargo such as ore or coal (for example), the bulk cargo is unloaded at a rail yard. At some rail yards, unloading equipment is deployed at the rail yard for controllably interacting with the train for dumping the bulk cargo. For example, when trains enter mining unloading equipment, they may be moved into position via an external indexing arm. In certain cases, external forces (wind, grade, etc.) can cause the train to move slightly out of position once the indexing arm retracts. This can lead to impacts between the train and the unloading equipment, and the possibility of the train being in contact with the unloading equipment with a sufficient degree of force to prevent the unloading equipment from functioning properly.
As will be appreciated, it may be desirable to provide a method and apparatus to reposition a train at a rail yard, which is different from existing systems.